Sharpen your shucking skills, people: South Australian oyster season is here. Hong Kong imports 67 percent of all Australia’s seafood, so you'll be spoiled for choice across the city. So what makes a great oyster? We asked a panel of experts for the low-down on the perfect specimen.

Are all oysters made equal?

There are three broad classifications: Pacific, Olympia and Atlantic. Each grouping is then further broken down by the shore from which the oysters are harvested, and graded by age and size. Yearlings are the youngest at a year old and the smallest at four-six centimeters long. Bistro oysters are three years old and 5cm-7cm. Plate oysters are also three years old, but larger at 6cm-9cm. And the king daddy of oysters are the "standard" grade: four years old and 9cm-11cm. But bigger doesn't always mean saltier (brinier) because a small oyster can pack a punch.

What are the qualities of an excellent oyster?

Connoisseurs describe oysters by their texture, degree of sweetness/salinity and mineral and marine plant flavors. Everyone agrees they must be fresh, and that a fishy smell is not good. Oyster importer Kathy Kingston says a moist, sweet-smelling shellfish is a must. And chef Dieter Lengauer recommends diners "smell each and every one." Our experts agree that the liquor (seawater inside the oyster) should be intact when served so the oysters are "swimming" in it. Conrad hotel assistant manager Giovanni Viterale says the shells should be kept closed until exposed to direct hear or the shucker's knife. For hotel food and beverage manager Jens Corder, the best oysters are high in mineral flavors.

Do oysters go in and out of season or are they mostly farmed these days?

Most oysters are farmed and all oysters are edible all of the time, but they still go in and out of season because they taste better in certain conditions. "Oysters are seasonal in that they breed in summer and during this time their meat is mushy in texture and warmer waters are higher in bacteria. Therefore people tend to eat oysters cultivated in winter months only," Corder explains. The general rule is that they are best when the outside temperature is below 20 degrees Celsius, and the most favorable conditions are 1-5 degrees C. Australian oysters are in season March to September, and French oysters from September to March.

Is there any danger in eating raw oysters?

There is as much danger eating oysters as there is eating raw lettuce, says JW Marriott executive sous-chef Danio Galli. If a food is contaminated with certain herbicides, bacteria, pesticides and metals, cooking will do nothing to cleanse it. "Raw oysters must not be consumed by very old and very young people or people with compromised immune systems," says Langham hotel's executive sous-chef Alain Hui. "Several organisms occur in shellfish that are harmless to the creature but are very dangerous to humans. Though fully cooked shellfish is recommended to lessen the chance of bacterial infection, oysters from clean, cold waters have few occurances of infectious organisms."

Do they have any nutritional value?

Oysters are one of the most nutritionally well-balanced foods, containing protein, carbohydrates and lipids. The US National Heart and Lung Institute says oysters are ideal for inclusion in low-cholesterol diets. The shellfish are an excellent source of vitamins A, B1 (thiamin), B2 (riboflavin), B3 (niacin), C (ascorbic acid) and D (calciferol). Four or five medium-sized oysters supply the recommended daily allowance of iron, copper, iodine, magnesium, calcium, zinc, manganese and phosphorus.

With sauce or without?

"Let people decide how to eat them," Kingston says. "If they like sauce, fine, but the experts taste them au naturel when grading them." True connoisseurs, she says, consume them as they come from the sea. Lobster Bar & Grill chef Leung Wing-yeung says: "There are also two classic sauces to be served with raw oysters. The first is a mignonette sauce with shallots and vinegar, and the second is a chili sauce. Oysters can also be poached, marinated, fried, grilled or baked."

And to drink?

"Champagne can be the perfect marriage," Leung says. "But it is not always necessary to serve expensive white wine with oysters. Try dry Spanish sherry, which is perfect with all shellfish, especially oysters; a Riesling from Alsace which is bone dry; or a Chardonnay, whether Californian, French or Australian. Remember you are trying to complement the distinctive seaweedy, salty and mineral tastes, with which the wine will have to compete."

Does anyone still eat Hong Kong oysters?

Oysters are still harvested at low tide in Lau Fau Shan and elsewhere, but few people eat them raw. Kingston points out: "People still eat HK oysters but they are not in good condition owing to heavy metals in the water and, most times, e-coli from fecal contamination and industrial poisons."

Final thoughts?

"Oysters are alive and each one is an individual," Kingston says. "They will not always look and taste exactly the same time after time. Oysters are very strong and live under grim conditions. Also anyone who claims to import daily is not being forthright because no one works seven days a week in the oyster export areas."

Oysters From Oz

Kathy Kingston explains how to tell a Franklin Harbour oyster from a Coffin Bay.
Point Douglas yearling: small, dense meat, mildly salty, long sweet finish
Coffin Bay standard: medium salty, crisp, neutral finish
Smoky Bay bistro: very salty, a little creamy, slight iodine finish from the water
Franklin Harbour bistro: rather salty, earthy, very firm meat
Franklin Harbour plate: similar to the bistro, just more of it - a pretty big mouthful

Did You Know...?

• "The record for shucking oysters is held by Frenchman Marcel Lesoille, who shucked 2,064 oysters in one hour. Also, George Pauling (a 19th-century South African railway builder), whose favorite parlor trick was to pick up a horse and carry it around his billiards table, was alleged to have shared with two friends a breakfast of 1,000 oysters and eight bottles of champagne," according to Chef Dieter Lengauer.
• They are low in calories, with about 12 in a small oyster.
• Oysters change sex one or more times during their lifespan. "There is no way of telling male oysters from females by examining their shells," Leung says. The gonads, organs responsible for producing both eggs and sperm, surround the digestive organs and are made up of sex cells, branching tubules and connective tissue.
• The tiny, dime-sized crab Pinnotheres ostreum sometimes found in oysters has evolved to live inside the shell. They are relatively rare and much sought after by gourmands.
• Pearls develop in oysters when foreign material becomes trapped inside the shell. The oyster responds to the irritation by producing nacre (a combination of calcium and protein) which coats the foreign material and over time produces a pearl.

The "R" Myth

According to folklore that oysters should be eaten only in months spelled with an "r" - March, April, September, October, and so on. But experts have been trying to educate people that oysters can be eaten year-round. The notion that oysters should not be eaten in the northern hemisphere summer - May-August - was started in the days when oysters where shipped without adequate refrigeration and could spoil.

Oyster-Friendly Wines

Martin Kniss recommends: Domaine de la Fruitiere 2003 Muscadet Sevre Et Maine, $320, at Cafe Deco
Colin Fung recommends: Oyster Bay Sauvignon Blanc, from New Zealand, $320, DotCod and HK Cricket Club
Giovanni Viterale recommends: Marco Felluga pinot grigio (Italy), $650 at Nicholini's and Brasserie on the 8th.